1. Field of the Invention
The present invention relates to a continuously curved drawbar adapted to be mounted in a receiver hitch for extending the bed and enhancing load carrying capacity of a transport vehicle. More particularly, the present invention relates to a curved drawbar adapted to be mounted in a receiver hitch for supporting a T-bar for carrying long lengths of building materials. The same drawbar, however, has other utilities.
2. Brief Description of the Prior Art
A number of different bed extenders have been proposed for carrying items having a length greater than the bed length of a vehicle. Some of these devices are described in U.S. Pat. No. 5,678,743 to Johnson et al., U.S. Pat. No. 5,458,389 to Young and U.S. Pat. No. 5,451,088 to Broad. With these devices it is possible to extend the bed between five and six feet from the receiver hitch and stay within feasible load limits.
In the Young patent, the drawbar is straight, five and one-half feet long and constructed of two-inch by two-inch by quarter-inch square steel tubing. Even without loading, which will cause the drawbar to sag slightly, the distal end of the drawbar may strike the ground when the front wheels of the vehicle are higher than the rear as when the vehicle backs down an inclined driveway into a street or goes over a speed bump, railroad track or the like. Both Johnson et al. and Broad address this problem by providing an angled drawbar that is elevated at its distal end above the receiver hitch. In both Johnson et al. and Broad, the drawbar is formed from cut sections of square steel tubing which are welded together so that the drawbar is upwardly directed. The Johnson et al. construction has gussets for reinforcing each angled joint.
When a load is applied on the distal end of the drawbar, all of the above-mentioned bed extenders deflect slightly, this being a more serious problem in the Young construction which has poor ground clearance even when not loaded. With the Johnson et al. and Broad extenders, as the drawbar deflects, the top of the drawbar is put under tension and the bottom is put under compression, which stresses are concentrated at the joints, the Johnson et al. construction being reinforced at those points. The cut-and-weld angled drawbars described by Johnson et al. and Broad are stiff such that when a loaded vehicle is driven over a rut, speed bump, railroad track or the like, the jolt (i.e., high-load impact) caused by the load on the T-bar is transferred through the drawbar to the receiver hitch. While the Johnson et al. bed extender is designed to withstand these forces, it would be desirable if the drawbar absorbed part of them. The stiffness of the angled drawbars also causes them to be permanently bent under some circumstances.
There are other opportunities for improvement. While the cut-and-weld drawbars of Johnson et al. and Broad are an improvement over the straight drawbar shown in the Young patent, they are more expensive to make because of the labor in the welds. It would be desirable, therefore, to have a drawbar that is upwardly angled, providing for ground clearance and deflection, without having the welds.